Correction wording flood risks for the Netherlands in IPCC report

In the 2007 IPCC report by the Working group 2 (Climate change 2007: Impacts, adaptation and vulnerability) a mistake has entered the text that was supplied by the Netherlands Environmental Assessment Agency, regarding the risks of flooding for the Netherlands. In the chapter on Europe, on page 547, it says that 55 per cent of the Netherlands is below sea level (‘The Netherlands is an example of a country highly susceptible to both sea level rise and river flooding because 55% of its territory is below sea level’). This should have read that 55 per cent of the Netherlands is at risk of flooding; 26 per cent of the country is below sea level, and 29 per cent is susceptible to river flooding. Examples of the latter are the near floodings, in the mid-1990s, of areas along the rivers Meuse and Waal – areas that are well above sea level.

The Netherlands is sensitive to climate change. Sea level rise as well as peak river discharges require precautionary measures. The incorrect wording in the IPCC report does not affect this conclusion.

Research continuously improves the insights with respect to possible flooding scenarios in specific areas (e.g. the project ‘Mapping safety in the Netherlands’ (Veiligheid Nederland in Kaart), www.projectvnk.nl). On this subject, the Netherlands Environmental Assessment Agency very recently published a study on flood-risk zones within the Netherlands’ (Overstromingsrisicozonering in Nederland).

Additional information: map of flood-prone areas

The map shows the areas within the Netherlands that lie below Amsterdam Ordnance Datum (NAP), as well as the areas that are susceptible to flooding. Based on the current contour map and spatial planning of the Netherlands, we can state that:

26% of the Dutch land surface is below NAP;

59% of the Dutch land surface (i.e. excluding the Wadden Sea, the IJsselmeer and other open waters) is susceptible to flooding. This 59% encompasses the areas both within and outside the dyke rings, the so-called ‘river foreland’;

55% of the Dutch land surface is located within the dyke rings, and is protected by dunes, dykes, dams and artificial structures

4% of the Dutch land surface is situated outside the dyke rings and, therefore, is not protected by dunes, dykes, dams or artificial structures.

These figures have been calculated in a cooperation between the Netherlands Environmental Assessment Agency and the Directorate-General for Public Works and Water Management. The percentages have been determined using the Geographical Information System (GIS) to calculate the surface areas. The data used in these calculations have been obtained from 'Actueel Hoogtebestand Nederland (a digital contour map of current heights of all of the Netherlands) of the Dutch Ministry of Transport, Public Works and Water' Management, and have been combined with the land statistics from Statistics Netherlands (CBS), and the database on dyke rings of the Directorate-General for Public Works and Water Management.

Flooding patterns differ per region

The risk of flooding is not equally divided over the flood-prone areas. The way a flood occurs in actual practice, depends on local circumstances and is largely determined by differences in height within a certain area, and for instance the presence of secondary dykes, construction of roads, and railway lines. Through further research on possible flooding scenarios in specific areas, insights into the risks of flooding are increasingly gained. In the study ‘The Netherlands in the Future’ (MNP, 2007), regional differences between flooding scenarios have already been included in, for example, calculations of economic damages and human casualties. On this subject, the Netherlands Environmental Assessment Agency very recently published a study on flood-risk zones within the Netherlands.